Jesús Alvarado-Ortega

Isotopic composition of low-latitude paleoprecipitation during the Early Cretaceous

The response of the hydrologic cycle in global greenhouse conditions is important to our understanding of future climate change and to the calibration of global climate models. Past greenhouse conditions, such as those of the Cretaceous, can be used to provide empirical data with which to evaluate climate models. Recent empirical studies have utilized pedogenic carbonates to estimate the isotopic composition of meteoric waters and calculate precipitation rates for the AptianAlbian. These studies were limited to data from mid- (35°N) to high (75°N) paleolatitudes, and thus future improvements in accuracy will require more estimates of meteoric water compositions from numerous localities around the globe. This study provides data for tropical latitudes (18.5°N paleolatitude) from the Tlayua Formation, Puebla, Mexico. In addition, the study confi rms a shallow nearshore depositional environment for the Tlayua Formation. Petrographic observations of fenestral fabrics, gypsum crystal molds, stromatolitic structures, and pedogenic matrix birefringence fabric support the interpretation that the strata represent deposition in a tidal fl at environment. Carbonate isotopic data from limestones of the Tlayua Formation provide evidence of early meteoric diagenesis in the form of meteoric calcite lines. These trends in δ 18 O versus δ 13 C

Revision of Recent Investigations in the Tlayúa Quarry

The Tlayua Quarry in Tepexi de Rodriguez, Puebla, Mexico, is one of the most important localities in the New World because of its uniquely rich biota. For the last twenty years, its exceptionally well-preserved fossil content and its taphonomical and paleoecological implications have caught the attention of many geologists and paleontologists since this Lagerstatte represents an important new asset in Mexican Paleontology. In this paper, we review all the recent investigations related to a development of the paleoecological models to explain the extraordinary conservation of the rich and diverse fossil assemblage of Tlayua.

Description and relationships of a new ichthyodectiform fish from the Tlayúa Formation (Early Cretaceous: Albian), Puebla, Mexico

Abstract A new species is described and proposed as a new genus and family belonging to the Order Ichthyodectiformes. The specimens referred to this taxon were collected in limestones of the Middle Member of the Tlayúa Formation of Albian age, near Tepexi de Rodríguez, Puebla, central Mexico. This new species shows a unique combination of primitive and derived characters. Its head and body proportions resemble those of other Cretaceous ichthyodectiforms, but its parietals are unfused and the caudal fin has three epurals and five uroneurals; it is also characterized by an unusually high total vertebral count, which comprises 78–80 centra, and areas of crowded teeth in the dentary and maxilla.

TRIPLOMYSTUS APPLEGATEI, SP. NOV. (TELEOSTEI: ELLIMMICHTHYIFORMES), A RARE "TRIPLE ARMORED HERRING" FROM EL ESPINAL QUARRY (EARLY CRETACEOUS), CHIAPAS, SOUTHEASTERN MEXICO

Abstract Triplomystus applegatei, sp. nov., is described as a new clupeomorph fish belonging to the order Ellimmichthyiformes, based on a single specimen collected from the Early Cretaceous (Albian) limestones of El Espinal quarry, near Ocozocuautla de Espinosa, Chiapas, southeastern Mexico. T. applegatei is differentiated from the other two species of the genus on the basis of body proportions and meristic data, as well as a peculiar development of a complex shape and articulation between the last scutes in the posterodorsal series. This species extends the geographical and geological domain of this genus from the Cenomanian Eastern Tethys Sea to Albian western Tethys Sea.

A New Genus of Ionoscopiform Fish (Halecomorphi) from the Lower Cretaceous (Albian) Lithographic Limestones of the Tlayúa Quarry, Puebla, Mexico

Abstract Quetzalichthys perrilliatae n. gen. and sp. is described based on five specimens from Lower Cretaceous (Middle-Upper Albian) limestones of the Tlayúa Quarry, near Tepexi de Rodríguez, Puebla, Mexico. This new taxon displays the diagnostic characters of Ionoscopiformes, which consequently designate it as a new member of this order of Mesozoic fishes. Additionally, Quetzalichthys n. gen. shares several derived characters with Ionoscopus and Oshunia, including the presence of more than 15 supraneurals, solid and well-ossified monospondylous vertebrae with two lateral longitudinal oval fossae, thin scales of the amioid type, and the ventral surface of some circumorbital bones being intensely pitted. Quetzalichthys perrilliatae is characterized by three unique characters: 26 abdominal centra, 21 principal dorsal fin rays, and two supraorbitals. Additionally, its unpaired fins and tail show conditions intermediate to those found in Ionoscopus and Oshunia. A cladistic analysis of Ionoscopiformes, including both taxa found in the Tlayúa Quarry (Quetzalichthys and Teoichthys), identifies two monophyletic families within the order, Ophiopsidae (including Ophiopsis, Macrepistius, Teoichthys) and Ionoscopidae (involving Ionoscopus, Oshunia, and Quetzalichthys).

A fossil stemmiulid millipede (Diplopoda: Stemmiulida) from the Miocene amber of Simojovel, Chiapas, México

A fossil millipede representative of the order Stemmiulida is described on the basis of a well-preserved adult female trapped in amber from the Miocene of Simojovel, Chiapas, south-eastern México. The fossil specimen is named as Parastemmiulus elektron, a new genus and species. As observed in extant stemmiulids, this fossil shows a reduced number of ocelli, the distal larger than the proximal, as well as a total of 46 trunk segments including 2 apodous segments in front of the telson. The head of this ancient stemmiulid has three ocelli and a Tömösváry organ, characteristics not reported before in Stemmiulida, requiring the diagnosis of the order to be emended.http://zoobank.org/urn:lsid:zoobank.org:pub:361400A8-37D4-421F-B4FD-A0AE63BE538C

Teoichthys brevipina, sp. nov., A New Ophiopsid Fish (Halecomorphi, Ionoscopiformes) from the Lower Cretaceous Tlayúa Formation, Central Mexico

SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

RHYNCHODERCETIS REGIO, SP. NOV., A DERCETID FISH (TELEOSTEI: AULOPIFORMES) FROM VALLECILLO, NUEVO LEÓN STATE, NORTHEASTERN MEXICO

Abstract Description of Rhynchodercetis regio, sp. nov., from Upper Cretaceous (Turonian) sediments of Vallecillo, State of Nuevo León, northeastern Mexico is based on three specimens. Rhynchodercetis regio differs from the other species of Rhynchodercetis in the exclusive combination of characters that includes the proportions of the head with its standard length, the length of the preorbital area, and the presence of an interopercle and a short mandibule. The occurrence of this fish in Mexico expands the known distribution of Rhynchodercetis in North America during the Late Cretaceous, from the Canadian portion of the Interior Sea to Mexico, in the western Tethys area.

Late Jurassic marine vertebrates from Tlaxiaco, Oaxaca State, southern Mexico

This paper provides the first geological and paleontological data of Yosobé and La Lobera, two Late Jurassic vertebrate localities; both localities are part of the marine deposits of the Tlaxiaco Basin, near Tlaxiaco, Oaxaca, Mexico. La Lobera may be included in Cerro de Titania, a historical invertebrate locality inaccurately described, whose Oxfordian-Early Kimmeridgian limestone and marl strata are informally known as “Caliza con Cidaris.” La Lobera contains the typical “Caliza con Cidaris” fossils and the remains of a single fish attributable to the genus Scheenstia. Yosobé is a fossiliferous outcrop belonging in the Late Jurassic (Kimmeridgian-Tithonian) bituminous shale strata informally known as Sabinal formation. The fossil assemblage from Yosobé includes microfossils, plants, invertebrates, and vertebrates, many of which are totally or partially tridimensionally preserved within nodules. Yosobé is the most important vertebrate locality along the entire Tlaxiaco Basin due to a highly abundant and diverse grouping of fishes and reptiles. The fossil assemblage from Yosobé reported in this paper includes the first and most inclusive regional record of taxa such as the first North American Pleuropholidae fish, the first Mexican Jurassic Planohybodus shark, the most complete specimens of the pycnodont Gyrodus in Mexico and the Caribbean, ichthyosaurs, thalattosuchian crocodyliforms, turtles, and pliosaurids in a single locality at the Western Tethys Sea Domain and the Hispanic Corridor. Present and future descriptive and systematic studies on some fossils from these localities may have important paleobiogeographic and phylogenetic implications worldwide. Jesús Alvarado-Ortega. Instituto de Geología, Universidad Nacional Autónoma de México, Circuito de la Investigación S/N, Ciudad Universitaria, Delegación Coyoacán, Distrito Federal, 04510 México; alvarado@geologia.unam.mx (Corresponding author) Jair Israel Barrientos-Lara. Posgrado en Ciencias Biológicas, Instituto de Geología, Universidad Nacional Autónoma de México, Circuito de la Investigación S/N, Ciudad Universitaria, Delegación Coyoacán, Distrito Federal, 04510 México; j4ir@me.com Luis Espinosa-Arrubarrena. Instituto de Geología, Universidad Nacional Autónoma de México, Circuito de la Investigación S/N, Ciudad Universitaria, Delegación Coyoacán, Distrito Federal, 04510 México; espinosa@geologia.unam.mx María del Pilar Melgarejo-Damián. Posgrado en Ciencias Biológicas, Instituto de Geología, Universidad PE Article Number: 17.1.24A Copyright: Society for Vertebrate Paleontology June 2014 Submission: 28 December 2013. Acceptance: 12 June 2014 Alvarado-Ortega, Jesús , Barrientos-Lara, Jair Israel, Espinosa-Arrubarrena, Luis, Melgarejo-Damián, María del Pilar. 2014. Late Jurassic marine vertebrates from Tlaxiaco, Oaxaca State, southern Mexico. Palaeontologia Electronica Vol. 17, Issue 1;24A; 25p; palaeo-electronica.org/content/2014/773-tlaxiaco-jurassic-vertebrates ALVARADO-ORTEGA: TLAXIACO JURASSIC VERTEBRATES Nacional Autónoma de México, Circuito de la Investigación S/N, Ciudad Universitaria, Delegación Coyoacán, Distrito Federal, 04510 México; pilar_melgarejo@yahoo.com

Magnetostratigraphy of the lower cretaceous strata in Tlayúa Quarry, Tepexi de Rodriguez, state of Puebla, Mexico

A stratigraphic sequence of magnetic polarity reversals consisting of nine magnetozones is recognized in Early Cretaceous sedimentary strata in the Tlayúa Quarry of Tepexi de Rodriguez, state of Puebla. Combined with biostratigraphic age assignments using ammonites that apparently belonging to the Albian, the geomagnetic polarity sequence can be correlated with the middle part of chron C34n (C34n.1n-C34n.2n chrons, with an age of 100–105 Myr), the Cretaceous long normal interval. The magnetic properties and characteristic remanence of magnetization are dominated by soft and hard coercivity magnetic minerals. Rock-magnetic properties and a positive reversal test suggest that remanence is primary. The section displays both reverse and normal polarities with mean directions: D=344.9°, I=32.4°, k=21, a95=4.2° and D=149.4°, I=−36.6°, k=17, a95=8.7°, respectively. Comparison with the North American apparent polar wander path indicates tectonic stability of the region since the Cretaceous.